Epidemiology

The epidemiology of salivary gland tumours is not well documented {2053}. In many studies the data are limited, as some are restricted to parotid gland neoplasms or tumours of major glands. In addition, most salivary gland tumours are benign and some cancer registries have only included malignant tumours. One study specifically excluded Warthin tumour, which is the second most common benign salivary neoplasm {698}. In addition, several investigators felt that their quoted incidence figures were an underestimate, particularly for benign tumours {963,1471,2053}. The global annual incidence when all salivary gland tumours were considered varied from 0.4-13.5 cases per 100,000 population {669}. The frequency of malignant salivary neoplasms ranged from 0.4-2.6 cases per 100,000 population {1353,1960,2053,2503}. In the United States, salivary gland malignancies accounted for 6% of head and neck cancers, and 0.3% of all malignancies {2167}. There is also some geographic variation in the frequency of tumour types. In studies of patients from Denmark and parts of Pennsylvania, about 30% of all parotid tumours were Warthin tumours, a sevenfold increase of the expected frequency {1765,2075}. The reported frequency of mucoepidermoid carcinomas among British patients (2.1%) is much lower than the worldwide range of 5-15% {703,704, 1772,2580}. There was a very high reported incidence of salivary gland tumours in North American Inuits from 1950-1966 {1087,2255}. This was almost exclusively due to lymphoepithelial carcinomas that formed 25% of all malignancies in this population. Since then there has been a significant decline in the relative frequency of this tumour. A survey of different ethnic groups in Malaysia showed a higher frequency of salivary tumours in Malays than Chinese or Indians {1551}. Another study showed variations in the incidence of salivary tumours amongst different ethnic groups according to their city of residence {1705}. It should be noted that in some series malignant lymphoma and metastatic disease represent about 9% of major gland tumours, highlighting the need to include these neoplasms in differential diagnostic considerations {669,1916}.

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